In fuel-cell-assisted transport systems, so-called chemical reformers may be used to recover the necessary hydrogen from hydrocarbon-containing fuels such as, for example, gasoline, ethanol, or methanol. Secondary combustion devices are used for heat generation, in particular in cold-start phases.
All the substances required by the reformer for execution of the reaction, for example air, water, and fuel, are conveyed to the reaction region ideally in a gaseous or at least atomized state. But because water and the fuels, for example methanol or gasoline, may preferably be present in liquid form on board the transport system, they must first be prepared shortly before they arrive at the reaction region of the reformer or the secondary combustion device. This may necessitate, for example, a dosing device that is capable of making the corresponding quantities of fuel or other substances available in finely atomized form.
Apparatuses for dosing fuels into reformers are discussed, for example, in U.S. Pat. No. 3,971,847. Here the fuel is fed in, by metering devices relatively remote from the reformer, through long delivery conduits and a single nozzle into a temperature-controlled material stream. The fuel first strikes impact panels that are disposed after the outlet opening of the nozzle and are intended to cause turbulence in and distribution of the fuel, and then travels into the reaction region of the reformer through a relatively long evaporation section that is necessary for the evaporation process. The long delivery conduit allows the metering device to be insulated from thermal influences of the reformer.
Particular disadvantages of the apparatuses discussed in the aforementioned document are the fact that below the operating temperature of the reformer, for example in a cold-start phase, atomization of the fuel occurs only insufficiently; and that the dosing device is configured in very complex and bulky fashion. Because of the relatively small reaction surface between fuel and oxidizer resulting in this context, combustion or chemical reaction occurs only slowly, and usually also incompletely.
The result is a distinct decrease in efficiency and a disadvantageous increase in pollutant emissions. Incomplete combustion or an incomplete chemical reaction usually results in the formation of aggressive chemical compounds that can damage the chemical reformer or secondary combustion device and cause deposits that can degrade functionality. The complex and bulky design in the nozzle region, where atomization is accomplished, results in high manufacturing and operating costs, especially because of poorer ease of assembly and greater susceptibility to error.